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In Praise of Physics

Both of us were intrigued by John Horgan's interesting analysis of Einstein's unique place in the history of science ("Einstein Has Left the Building," Jan. 1). Genius like that of Einstein or Newton or Archimedes is certainly very rare.

But we take exception to much of Horgan's characterization of contemporary physics. Horgan has repeatedly dismissed much of modern theoretical physics as "fantasy realms" and what he calls "ironic science," by which he means something like science fiction. For some reason he seems to think that reconciling quantum mechanics with Einstein's theory of gravity is a frivolous pursuit. Moreover, Horgan evidently sees the two of us as being on opposite sides of an imagined controversy. One of us (Leonard Susskind) may be his exemplar of an ironic scientist, and the other (Lawrence M. Krauss) a hero of the sensible opposition. But the fact is that there is little of substance that we disagree about.

In the first place, there have been a host of spectacular developments in physics since Einstein, many of which began as what Horgan might call "ironic science." The modern "Standard Model" of elementary particle physics, including our current understanding of the origin of mass itself, arose out of investigations of a formalism that was proposed for purely theoretical reasons associated with mathematical symmetries. Moreover, both of us feel that reconciling the conflict between gravity and quantum mechanics is one of the deepest problems in modern physics. While theoretical and experimental investigations in this area are extremely difficult, so that progress may be halting, the resolution of the conflict is likely to have major repercussions for our understanding of the tiniest elementary particles as well as the birth and evolution of the universe.

As for Horgan's bête noire of physics -- higher dimensions, or what he refers to as "hyperspace theories" -- he writes: "But pursuers of this 'theory of everything' have wandered into fantasy realms of higher dimensions with little or no empirical connection to our reality." That both of the present writers recognize that additional degrees of freedom of one sort or another are needed to characterize the physics of elementary particles may come as a surprise to Horgan. What the two of us may disagree about is what may be the likely physical and mathematical basis of this fact. But we both recognize that the mathematical spaces that we already deal with in describing the quantum theory of matter are in a certain sense more mathematically exotic than simple possible extra physical dimensions.

Horgan quotes one of us in supporting his negative viewpoint: "In his new book 'Hiding in the Mirror: The Mysterious Allure of Extra Dimensions, from Plato to String Theory and Beyond,' the physicist Lawrence Krauss frets that his colleagues' belief in hyperspace theories in spite of the lack of evidence will encourage the insidious notion that science 'is merely another kind of religion.' "

But the intended warning was not that hyperspace theories are religion, or that physicists should abandon ambitious goals. Rather the warning was simply that physicists have to be accurate and honest about the nature of our speculations, and in particular about the lack of progress thus far in making successful predictions that might be tested. Otherwise we risk reinforcing popular misconceptions about the nature of the scientific enterprise such as those that seem implicit in Horgan's essay.